old changes
MVVM Demo

model - a number set to 0
viewmodel - number from model, up command: increment number untill 5
view - datacontenxt set to viewmodel, label bound to number, button
command set to up

ref:
* source -
http://www.codeproject.com/script/articles/download.aspx?file=/KB/WPF/435478/MVVMSample.zip&rp=http://www.codeproject.com/Articles/435478/MVVM-Demo
* video tutorial -
http://www.lab49.com/wp-content/uploads/2011/12/Jason_Dolinger_MVVM.wmv
* lambda -
http://mfelicio.com/2010/01/10/safe-usage-of-inotifypropertychanged-in-mvvm-scenarios/